1. Field of the Invention
The present invention relates to a power line communication system, and in particular to a method for transmitting an adaptive multi-channel packet in a power line communication system.
2. Description of the Background Art
In the power line communication (PLC), a radio frequency communication signal of a few hundreds Hz to a few tens MHz is transmitted together with an alternating power to a power line supplying the alternating power having frequencies of 50 to 60 Hz to houses, and a private access device receives only the communication signal for communicating. In the PLC, since there are no needs a high-priced private line or basic network, it can be used as an external network for internet access or a local area network (LAN) such as a home LAN through the connection with a plug receptacle, so it is a convenient and economical communication network suitable. Home appliances such as a TV, VCR and computer generate a volume of load in the power line.
The PLC is performed in a fixed transmission speed by using a fixed frequency region of a PLC channel. When the channel has a good property, the PLC stably obtains a wanted performance. However, when serious attenuation or distortion is generated in the PLC channel due to a load having a poor channel property, the communication quality is considerably deteriorated. The communication cannot be performed in the worst case.
When the PLC where a property of the channel is remarkably varied according to a frequency like the power line channel is performed by employing a fixed frequency, if a fixed frequency band has a poor property, a communication failure is generated.
Accordingly, it is an object of the present invention to provide a method for transmitting an adaptive multi-channel packet in a power line communication system which can transmit the packet in an optimal speed suitable for a multi-channel environment, without requiring pre-communication for multi-channel adaptation among the nodes of the power line communication system.
To achieve the above object of the present invention, there is provided a method for transmitting an adaptive multi-channel packet in power line communication system comprising the steps of: (a) transmitting a packet from a first node to a second node with a predetermined transmission speed through a power line by using a multi-channel in communication from the first node and the second node; (b) checking an error of the packet transmitted from the step (a) in the second node, thereafter loading the check result to the packet and transmitting it to the first node through the power line by using a multi-channel; (c) checking the result of the packet transmitted from the step (b) in the first node, and storing the check result as a database; (d) transmitting the packet to the second node with any one among the current, downgraded or upgraded transmission speeds through the power line according to the packet transmission success/failure information stored as the database in the step (c); and (e) transmitting the packet with a stable transmission speed according to the multi-channel by performing repeatedly the steps (b) to (d).
Preferably, the packet in the step (a) is a normal packet for transmitting system data and the packet in the step (b) is a control packet for transmitting packet error generation/non-generation information and its own address information.
Also, preferably, in the step (b), the error check of the packet transmitted from the first node through the power line with a predetermined transmission speed is performed by using a CRC(Cyclic Redundancy Check) method.
Preferably, the step (b) further comprises the steps of: (b1) checking the packet error by receiving the packet transmitted from the step (a) through the power line and thereafter when an error is generated in the packet as a result of the check, loading the packet error generation information and its own address information to the packet and transmitting it through the power line; and (b2) When an error is not generated in the packet as a result of the check in the step (b1), loading the packet error non-generation information and its own address information to the packet and transmitting it through the power line.
Also, in the step (c), the information is stored as a database in a media access controller (MAC) address.
Preferably, the database in the step (c) is periodically upgraded and a period is manually controlled according to a using environment.
Also, preferably, the step (d) further comprises the steps of: (d1) comparing the number of times of retransmission with a predetermined first reference value when the packet transmission fails according to the packet transmission success/failure information stored as a database in the step (c), retransmitting the packet to the second node through the power line with a predetermined transmission speed when the number of times of retransmission is smaller than the predetermined first reference value as the comparison result, and finishing the packet transmission when the number of times of retransmission is greater than the predetermined first reference value; (d2) comparing the number of times of transmission with a predetermined second reference value when the packet transmission is successfully performed according to the packet transmission success/failure information stored as a database in the step (c) and transmitting the packet to the second node through the power line in the current transmission speed at the next time when the number of times of transmission is smaller than the predetermined second reference value; (d3) comparing a transmission failure count value with a predetermined third reference value in the case that the number of times of transmission is greater than the predetermined second reference value as the comparison result of the step (d2) and thereafter transmitting the packet to the second node through the power line in a transmission speed downgraded by one step at the next time when the transmission failure count value is greater than the predetermined third reference value; (d4) comparing a transmission success count value with a predetermined fourth reference value when the transmission failure count value is smaller than the predetermined third reference value as the comparison result of the step (d3) and thereafter transmitting the packet to the second node through the power line in a transmission speed upgraded by one step at the next time when the transmission success count value is greater than the predetermined fourth reference value; and (d5) transmitting the packet to the second node through the power line in the current transmission speed at the next time in the case that the transmission success count value is smaller than the predetermined fourth reference value as the comparison result of the step (d4).